Double Wall Plate Heat Exchanger

Abstract

The present invention discloses a plate heat exchanger (100) including a plurality of double-walled plates formed with ridges (R) and grooves (G) that provide contact points between adjacent heat exchanger elements (110, 120) forming flow paths for fluid to exchange heat. The flow paths are in selective fluid communication with each other through port openings. Each of the heat exchanger elements (110, 120) comprises at least two joined plates, and leakage channels are formed between the plates of each heat exchanger element (110, 120) for fluid leaking from the flow paths. The plates are provided with cooperating ridges (190) and depressions (200) that form leakage channels (210) that extend across the ridges and grooves between the plates of each heat exchanger element (110, 120). At least one connection space is formed between the plates for connecting leakage channels in the same heat exchanger element (110, 120), and each connection space is connected to a leakage port.

Description

[Technical field]

[0001] The present invention relates to a double-wall plate heat exchanger. More specifically, the present invention relates to a double-wall plate heat exchanger including a plurality of double-wall plate heat exchanger elements, the double-wall plate heat exchanger elements being formed with ridges and grooves providing contact points between at least some intersecting ridges and grooves of adjacent double-wall plate heat exchanger elements under the formation of flow paths between the double-wall plate heat exchanger elements for fluid to exchange heat, the flow paths being selectively in fluid communication with each other through port openings of the double-wall plate heat exchanger elements, each of the double-wall heat exchanger elements including two plates, the plates being formed with ridges and grooves for forming the ridge and groove pattern of the double-wall heat exchanger elements, and leakage channels being formed between the plates of each double-wall plate heat exchanger element for fluid leaking from the flow paths.

[0002] Dual-wall plate heat exchangers are commonly used to avoid leakage of one fluid into another fluid within the heat exchanger. For example, such dual-wall plate heat exchangers are useful in heat exchange applications involving fluids for human consumption, such as liquid foods, or fluids that may result in undesirable chemical reactions when mixed. Dual-wall plate heat exchangers may also be useful where it is desirable to detect leakage of one fluid into the other. [Background technology]

[0003] Several different types of brazed double-walled plate heat exchangers can be found in the prior art. As known to those skilled in the art, such heat exchangers include a number of double-walled heat exchanger elements formed by two joined plates, said plates being formed with ridges and grooves to form the ridge and groove pattern of the double-walled heat exchanger elements, with leakage channels formed between the plates of each double-walled plate heat exchanger element to collect fluid leaking from the flow passages and direct it to the periphery of the plate.

[0004] One problem with prior art double wall plate heat exchangers is that they can be inefficient and unreliable.

[0005] Another problem with such prior art double wall plate heat exchangers is that leaks can be difficult to detect.

[0006] Yet another problem with such prior art double wall plate heat exchangers is that they can be difficult and complicated to manufacture. Summary of the Invention

[0007] It is an object of the present invention to overcome or at least mitigate the above mentioned problems and to provide a reliable and efficient double wall plate heat exchanger which is easy to manufacture and has easy leak detection.

[0008] The present invention relates to a double-walled plate heat exchanger comprising a plurality of double-walled heat exchanger elements formed with a pattern of ridges and grooves providing contact points between at least some intersecting ridges and grooves of adjacent heat exchanger elements under the formation of flow paths between the double-walled plate heat exchanger elements for fluid to exchange heat, said flow paths being in selective fluid communication with each other through port openings of said double-walled heat exchanger elements, each of said double-walled heat exchanger elements including at least two mating plates, said plates being formed with ridges and grooves to form the pattern of ridges and grooves of said double-walled heat exchanger elements. Also, between the plates of each double-walled plate heat exchanger element, a leakage channel is formed for the fluid leaking from the flow path, the plates being provided with cooperating elevations and indentations forming a leakage channel extending across the ridges and grooves between the plates of each double-walled heat exchanger element, and at least one connection space is formed between the plates of each double-walled heat exchanger element. The connection space connects the leakage channels in the same double-walled heat exchanger element, and the connection space is connected to a leakage outlet. The combination of the leakage channel across the ridges and grooves and the connection space connecting the leakage channels results in that the leakage fluid is collected in an efficient manner and can be directed, for example, towards a single leakage outlet or several leakage outlets at one or more desired locations, and the detection of the leakage can be facilitated. Thus, the connection space can be connected to a specific leakage area, whereas the leakage of the prior art is a non-defined leakage or is diffuse. The leakage channels connected to the connection spaces according to the invention also result in the double-wall plate heat exchanger being efficiently and reliably manufactured by brazing, since the brazing material can be applied in a simple manner and stop-offs can be eliminated. The leakage channels can be relatively narrow to provide efficient heat transfer.

[0009] The connection space(s) can extend along the ridges and / or grooves of the plate. Thus, the leakage channels arranged across the ridges and grooves are connected to each other through the connection space extending along the ridges and / or grooves, and fluid from any leakage channel can reach a single or several leakage outlets through the connection space. The connection space(s) can be formed by ridges formed at a lower height than the corresponding ridges of the adjacent plates, and the connection space is formed between the lower ridges that are received in the higher ridges (or grooves as well). Thus, the connection space is efficiently and reliably formed. Also, the connection space can be limited to one or a few in order to maintain a high efficiency of heat exchange. Thus, a large heat exchange area can be maintained, since several, most or almost all of the ridges and grooves do not have a connection space and are in contact with each other. Also, conventional brazing points can be provided between the ridges and grooves that are in contact with each other in the double-walled heat exchanger element, resulting in a robust heat exchanger.

[0010] The plates can be rectangular and the leaks can be located on the short sides, thus directing the leaking fluid to a single leak on the short side of the heat exchanger, making leak detection easier. The long sides of the plates can then be joined by conventional methods, such as continuous brazing on the long sides, in which case the heat exchanger can be stronger and more efficiently manufactured.

[0011] The plate may be provided with a peripheral skirt, and the skirts of three consecutive plates may be provided with openings forming a common leakage outlet from the leakage channels of two adjacent double-wall plate heat exchanger elements. For example, the openings may be aligned. The openings may be located on the short sides of the plate. Thus, leakage may be collected in one or several positions for easier and more reliable detection, while the main part of the periphery of the plate, for example the part including the entire long side, may be joined by brazing, providing a strong heat exchanger and efficient production.

[0012] The heat exchanger can be provided with a leak sensor, such as a conventional leak sensor. The leak sensor can be provided at a leak outlet, such as at a defined location or at several defined locations on the periphery of the heat exchanger, to achieve efficient and reliable leak detection. For example, the leak sensor can be attached to the periphery of the heat exchanger.

[0013] Further features and advantages of the invention will become apparent from the following description of embodiments, the accompanying drawings and the dependent claims.

[0014] The invention will now be described with reference to the accompanying drawings. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic exploded perspective view of an example of a plate heat exchanger. [Diagram 2] FIG. 2 is a schematic exploded perspective view of a plurality of double-wall plate heat exchanger elements according to one embodiment, each double-wall plate heat exchanger element including two plates. [Diagram 3] FIG. 3 is a schematic exploded perspective view of a first double-wall plate heat exchanger element and a second double-wall plate heat exchanger element according to one embodiment, the first double-wall plate heat exchanger element comprising a first and a second plate, and the second double-wall plate heat exchanger element comprising a third and a fourth plate. [Figure 4] FIG. 4 is a schematic front view of the double-walled heat exchanger element of FIG. [Diagram 5] FIG. 5 is a schematic cross-sectional view taken along line AA of FIG. 4, showing the flow paths between the double-wall plate heat exchanger elements and the leakage channels in each of the double-wall plate heat exchanger elements. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line BB in FIG. 4, showing a double-wall plate heat exchanger element partially along a portion of a leakage channel and partially along a portion without a leakage channel. [Figure 7] FIG. 7 is a schematic front view of a double-wall plate heat exchanger element. [Figure 8] FIG. 8 is a schematic cross-sectional view taken along line CC in FIG. 7, illustrating the connection spaces along the two ridges and two grooves according to one embodiment. [Figure 9] FIG. 9 is a schematic exploded perspective view of a portion of a double-wall plate heat exchanger element according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Referring to FIG. 1, a brazed plate heat exchanger 100 according to one embodiment is shown. The heat exchanger 100 is formed by stacking a plurality of first plate heat exchanger elements 110 and a plurality of second plate heat exchanger elements 120 to form the heat exchanger 100. For example, the heat exchanger elements 110, 120 are identical. Alternatively, the heat exchanger elements are not identical and the heat exchanger 100 is composed of at least two, three, or four different heat exchanger elements 110, 120. The heat exchanger 100 is a double-walled heat exchanger, with each of the heat exchanger elements 110, 120 including two plates joined together to form the heat exchanger elements 110, 120, as will be described in more detail below. Thus, the first heat exchanger element 110 is a first double-walled plate heat exchanger element and the second heat exchanger element 120 is a second double-walled plate heat exchanger element. For example, the heat exchanger 100 is a symmetric heat exchanger. Alternatively, the heat exchanger is an asymmetric heat exchanger, where the heat exchanger includes at least two different heat exchanger elements 110, 120.

[0017] The heat exchanger elements 110, 120 are made from sheet metal such as copper or stainless steel and are provided with a pressed pattern of ridges and depressions, for example, the heat exchanger elements are made from copper or austenitic stainless steel having a thickness of 0.1 to 2 mm.

[0018] In the illustrated embodiment, the ridges and recesses include ridges R and grooves G, whereby flow paths for fluids to exchange heat are formed between the heat exchanger elements 110, 120, which are stacked in a stack to form the heat exchanger 100 by providing contact points between at least some intersecting ridges and grooves of adjacent heat exchanger elements 110, 120. The pressed pattern of the plate in FIG. 1 includes a herringbone pattern. The pressed pattern may include any suitable pattern or combination of patterns. The pressed pattern is adapted to space the heat exchanger elements 110, 120 apart from each other, forming flow paths, except at the contact points. The ridges R and grooves G are elongated. For example, the ridges R and grooves G extend diagonally between a side, e.g., a long side, of the heat exchanger element 110, 120 and a centerline, e.g., a centerline extending between the short sides, to form a chevron, and the ridges and grooves continue on the opposite side, e.g., the opposite long side, e.g., at a mirror oblique angle. For example, the ridges R and grooves G extend between the opposing long sides in a herringbone pattern with a chevron in the middle.

[0019] Alternatively, the ridges R and grooves G extend obliquely in a straight line from one long side to the opposite long side.

[0020] In the illustrated embodiment, each of the heat exchanger elements 110, 120 is surrounded by a skirt S, which extends substantially perpendicular to the plane of the heat exchanger element and is adapted to contact the skirt of the adjacent heat exchanger element 110, 120 to provide a seal along the periphery of the heat exchanger or at least along a major portion of the heat exchanger. In the embodiment of Fig. 1, the skirt S is arranged continuously along both sides of the heat exchanger element 110, 120, for example along the two long sides in the case of a rectangular heat exchanger as shown. In the illustrated embodiment, the skirt S is also arranged continuously along one of the short sides of the heat exchanger element 110, 120.

[0021] The heat exchanger elements 110, 120 are provided with port openings 01-04 for the flow of heat exchanging fluids into and out of the flow paths. In the illustrated embodiment, the heat exchanger elements 110, 120 are arranged with a first port opening 01, a second port opening 02, a third port opening 03, and a fourth port opening 04. The areas surrounding the port openings 01-04 are provided at different levels such that selective communication between the port openings and the flow paths is achieved. In the heat exchanger 100, the areas surrounding the port openings 01-04 are arranged such that the first and second port openings 01 and 02 are in fluid communication with each other via several flow paths, and the third and fourth port openings 03 and 04 are in fluid communication with each other by adjacent flow paths. In the illustrated embodiment, the heat exchanger elements 110, 120 are rectangular with rounded corners and the port openings 01-04 are arranged near the corners. Alternatively, the heat exchanger elements 110, 120 are, for example, square with rounded corners. Alternatively, the heat exchanger elements 110, 120 are circular, elliptical or arranged in any other suitable shape, with the port openings 01-04 being distributed in an appropriate manner. In the illustrated embodiment, each of the heat exchanger elements 110, 120 is formed with four port openings 01-04. In other embodiments of the invention, the number of port openings may be more than four, i.e. six, eight or ten. For example, the number of port openings is at least six and the heat exchanger is configured to provide a heat exchange between at least three fluids. Thus, according to one embodiment, the heat exchanger is a three-circuit heat exchanger with at least six port openings, additionally arranged with or without at least one integrated suction gas heat exchanger.

[0022] The heat exchanger 100 according to Figure 1 includes a cover plate 130 and an end plate 140. For example, the cover plate 130 and the end plate 140 are of conventional design.

[0023] 2, a heat exchanger 100 comprising a plurality of heat exchanger elements 110, 120 is shown according to an embodiment, diagrammatically, without cover plates 130 and end plates 140, to show the structure of the heat exchanger elements 110, 120. Each heat exchanger element 110, 120 comprises a plurality of plates forming the heat exchanger element as a double-wall plate heat exchanger element. In the illustrated embodiment, the first heat exchanger element 110 comprises a first plate 150 and a second plate 160, and the second heat exchanger element 120 comprises a third plate 170 and a fourth plate 180, forming a double-wall structure of each of the heat exchanger elements 110, 120. For example, the first heat exchanger element 110 is formed by the first plate 150 and the second plate 160, and the second heat exchanger element 120 is formed by the third plate 170 and the fourth plate 180. The plates 150-180 are formed with ridges R and grooves G for forming the ridges R and grooves G of the heat exchanger elements 110, 120. The ridges R and grooves G of the plates 150-180 of the same heat exchanger element 110, 120 are received by each other, but the ridges R and grooves G of the heat exchanger elements 110, 120 are arranged to form flow paths between them. Thus, in the illustrated embodiment, the ridges R of the second plate 160 are received by the ridges R of the first plate 150 to form the first heat exchanger element 110, and the ridges R of the fourth plate 180 are received by the ridges R of the third plate 170 to form the second heat exchanger element 120. The double wall structure is for fluids leaking from the flow paths. The flow paths are arranged between the heat exchanger elements 110, 120 to perform heat exchange between the fluids flowing through the different flow paths. Flow paths are formed between the second plate 160 and the third plate 170. For example, there are no flow paths between plates of the same heat exchanger element 110, 120, there are no such flow paths between the first plate 150 and the second plate 160 of the first heat exchanger element 110, and there are no such flow paths between the third plate 170 and the fourth plate 180 of the second heat exchanger element 120. When a stack of plates 150-180 is brazed to form the heat exchanger 100, the plates 150-180 are joined to each other at brazed joints.

[0024] 3, the heat exchanger elements 110, 120 are shown in more detail according to one embodiment, where the plates 150-180 are formed with cooperating ridges 190 and recesses 200 that form leakage channels 210 for leakage of fluid from the flow paths. The ridges 190 and recesses 200 are distributed to provide a plurality of leakage channels 210 within the plates 150-180. The leakage channels 210 are arranged to collect fluid leaking from the flow paths, i.e., from the opposite side of the plate. Thus, the leakage channels 210 are arranged to collect fluid leaking through the plate, such as through holes in the plate, or to the opposite side of the plate due to a faulty or broken brazed joint, such as around the port openings 01-04 or at the peripheral skirt S. The leakage channels 210 extend across the ridges R and grooves G of the heat exchanger elements 110, 120. The leakage channels 210 are distributed on the surfaces of the plates 150-180. For example, the plates 150-180 are rectangular, and the leakage channels 210 are distributed across the width of the plates and extend in the longitudinal direction of the plates. Thus, there are gaps between adjacent leakage channels 210. For example, the plates are in contact with each other between the leakage channels 210 to provide efficient heat transfer. For example, the leakage channels 210 are relatively narrow, and thus the gap between them covers a larger area of ​​the plates than the leakage channels 210. In the illustrated embodiment, the leakage channels 210 extend substantially parallel to each other.

[0025] The leakage channels 210 of each heat exchanger element 110, 120 are connected to each other within the same heat exchanger element 110, 120 through at least one connection space 220. The connection space 220 connects the leakage channels 210 to the leakage outlets 230. For example, the connection space 220 connects the leakage channels 210 to a small number of leakage outlets, such as four or less leakage outlets or two or less leakage outlets. In the illustrated embodiment, the connection space 220 connects all leakage channels of the heat exchanger elements 110, 120 to a single leakage outlet 230. In the case of rectangular plates 150-180, the leakage outlet 230 is, for example, located on a single short side of each of the heat exchanger elements 110, 120 as shown. Alternatively, the leakage outlets are located on both short sides of the heat exchanger elements 110, 120. In the illustrated embodiment, the connection space 220 connects the leakage channels 210 to the leakage outlets 230 through two central leakage channels. Thus, the connection space 220 is disposed between a first pair of adjacent port openings 01, 03 and a second pair of adjacent port openings 01, 04, e.g., proximate to one of the pairs of adjacent port openings, and one or more central leakage channels 210 extend from the connection space 220 between the port openings of the pair of adjacent port openings and further to a leakage outlet 230. Thus, leakage fluid can be conducted from any of the leakage channels 210 to a leakage outlet 230, such as a single leakage outlet on a short side. The connection space 220 extends across and connects the multiple leakage channels 210, allowing leakage fluid to flow between the leakage channels 210.

[0026] In the illustrated embodiment, the leak 230 is formed by an opening in at least one skirt S of the plates of the heat exchanger elements 110, 120, so that fluid collected between the plates of the heat exchanger elements 110, 120 can exit the heat exchanger 100. For example, the skirts S of three consecutive plates, such as the first, second and third plates 150-170, are formed with leaks 230 in aligned positions to provide a common leak from the leak channels 210 of two adjacent heat exchanger elements 110, 120. The fourth plate 180 is formed, for example, with a continuous skirt S or at least one skirt without a corresponding opening to hold the leaking fluid, isolated from any fluid leaking from adjacent flow paths. Thus, any fluid leaking from one particular flow path can be collected in a single common leak 230, regardless of the location of the leak.

[0027] 4-6, the leakage channels 210 between the plates 150-180 in the same heat exchanger element 110, 120 are shown in more detail according to one embodiment. As seen in FIG. 5, the ridges 190 and the recesses 200 cooperate to form the leakage channels 210. FIG. 5 is simplified to better show the flow paths 210. The ridges 190 of every other plate, such as the first plate 150 and the third plate 170, facing the recesses 200 of other plates, such as the second plate 160 and the fourth plate 180, form the leakage channels 210 across the ridges R and the grooves G, so that the fluid leaking from the flow paths can be transported along one or more leakage channels 210, such as the leakage channel 210 close to the leakage, and, if necessary, through the connection space 220 to the leakage outlet 230. For example, the ridges 190 and depressions 200 are arranged in rows, such as substantially linear rows, in the longitudinal direction of the plate, as seen in FIG. 4. In FIG. 4, the ridges 190 of the grooves G of the first plate 150 according to one embodiment can be seen. For example, the ridges 190 and depressions 200 are arranged to provide at least one or two central leakage channels 210 extending along the plate between the first and second port openings 01, 03 and between the second and fourth port openings 02, 04. As seen in FIG. 6, the plates 150, 160 of the first heat exchanger element 110 and the plates 170, 180 of the second heat exchanger plate 120 contact each other in the area between the ridges 190 and depressions 200 forming the leakage channels 210 to provide efficient heat exchange between the fluids in the flow paths, which are indicated by reference numeral 240 in FIGS. 5 and 6. FIG. 6 is simplified for illustrative purposes. However, as can be seen in FIG. 6, the first and second plates 150, 160 contact each other in the area between the leakage channels 210, and the third and fourth plates 170, 180 also contact each other in the area between the leakage channels 210, with the flow path 240 being disposed between the second and third plates 160, 170.

[0028] 7-9, the connection space 220 according to one embodiment is shown in more detail. At least one connection space 220 is arranged to connect the leakage channels 210. For example, 1-10 connection spaces 220 are provided, such as 6 or less or 4 or less. According to one embodiment, two connection spaces are provided. The connection space 220 extends along the ridges R and / or grooves G and connects the leakage channels 210 extending in a direction transverse to the ridges R and grooves G. For example, the at least one connection space 220 is provided by forming one or more ridges R and / or one or more grooves G of a selected plate at a different height than the corresponding ridge(s) and / or groove(s) of the other plate, so that the connection space 220 extends along the gap formed therebetween.

[0029] For example, the connection space 210 is formed in several adjacent ridges R and / or grooves G, such as 2-10 or 2-6 or 4 adjacent ridges R and / or grooves G. As can be seen in the simplified FIG. 8, the connection space 220 is provided in that two grooves G of the first plate 150 are arranged at a lower height than the corresponding grooves G of the second plate 160, the second plate 160 being formed with two ridges R having a lower height than the corresponding ridges of the first plate 150. In FIG. 8, the first and second plates 150, 160 are shown. However, the principle of the connection space(s) 220 is similar for the third and fourth plates 170, 180. In FIG. 8, the connection space 220 is provided in that two ridges R of the second plate 160 are arranged at a lower height than the two corresponding ridges R of the first plate 150. Thus, the connection space(s) 220 are provided by the gaps between the plates along the ridges R and / or grooves G, and the leaking fluid can be transported through the connection space(s) 220 to the leakage channel 210 and further to the leakage outlet 230, regardless of where the leakage is located. For example, the connection space(s) 220 are formed by one or more ridges R and / or grooves G having a press depth smaller than the corrugation depth of the plate, for example 60-95% or 80-95% of the corrugation depth. The other ridges R and grooves G of the plates 150-180 are in substantially complete contact with each other, for example with a tight fit for efficient heat transfer. Thus, only a single connection space 220 or only a selected few connection spaces 220 are provided. For example, the connection spaces 220 are located adjacent to pairs of adjacent port openings 01-04 but not between pairs of adjacent port openings 01-04, so that the connection spaces 220 can connect the leakage channels 210 distributed over substantially the entire width of the heat exchanger elements 110, 120. For example, the last full-length ridge(s) R and / or groove(s) G are arranged to provide the connection space(s) 220 for connecting the leakage channels 210 and the leakage openings 230.Alternatively, multiple connection spaces 220 are distributed over the surface of the plate, connecting the leakage channels 210 at different positions in the longitudinal direction of the plate. Alternatively, the connection spaces 220 are formed by ridges and / or depressions in the plate, connecting the leakage channels 210.

[0030] An example of leakage flow is shown in Fig. 7 by the dashed arrow from the leakage point to the leakage outlet 230. The leakage point is indicated by a point, in this case a hole in the second plate 160, where fluid from the flow passage 240 between the second plate 160 and the third plate 170 enters between the second plate 160 and the first plate 150. The leakage fluid becomes directed to the nearest leakage channel 210, etc., formed by the cooperating ridges 190 and depressions 200. The leakage fluid can then flow freely and quickly along the leakage channel 210 to the connecting space 220, and the leakage fluid can flow from one leakage channel 210 to another leakage channel 210 that leads to the leakage outlet 230.

Claims

1. A double-wall plate heat exchanger (100) comprising a plurality of double-wall plate heat exchanger elements (110, 120), The heat exchanger elements (110, 120) are formed with a pattern of ridges (R) and grooves (G) that form flow paths (240) for fluid to exchange heat between adjacent heat exchanger elements (110, 120) and provide contact points between intersecting ridges and grooves of at least some of the adjacent heat exchanger elements (110, 120), the flow paths being in selective fluid communication with each other through port openings in the heat exchanger elements (110, 120), each of the heat exchanger elements (110, 120) comprising at least two joining plates (150-180) in which the ridges (R) and grooves (G) are formed to form the pattern of the ridges and grooves of the heat exchanger elements (110, 120), and leakage channels are formed between the plates of each of the heat exchanger elements (110, 120) for fluid to leak from the flow paths, said plates (150-180) are provided with cooperating ridges (190) and recesses (200) which form leakage channels (210) extending across said ridges (R) and said grooves (G) between said plates of each said heat exchanger element (110, 120); At least one connection space (220) is formed between the plates of each of the heat exchanger elements (110, 120), the connection space (220) connecting the leakage channels (210) in the same heat exchanger element (110, 120); A double-wall plate heat exchanger, characterized in that at least one said connection space (220) is connected to a leakage opening (230).

2. 2. The double-wall plate heat exchanger (100) according to claim 1, wherein at least one said connection space (220) extends along said ridges (R) and / or said grooves (G) of said plate.

3. 3. The double-wall plate heat exchanger (100) according to claim 1 or 2, wherein the connection space (220) is formed by forming at least one of the ridges (R) and / or at least one of the grooves (G) of a selected plate at a different height than the corresponding ridges and / or grooves of the other plate.

4. 4. The double-wall plate heat exchanger (100) of claim 3, wherein the connection spaces (220) are formed by one or more of the ridges and / or grooves in one of the plates of each of the heat exchanger elements being formed at a different height than the corresponding ridges and / or grooves in the other plate.

5. The double-wall plate heat exchanger (100) according to any one of claims 1 to 4, wherein each of the heat exchanger elements (110, 120) comprises eight or less of the connection spaces (220), six or less of the connection spaces, or four or less of the connection spaces.

6. The double-wall plate heat exchanger (100) according to any of the preceding claims, wherein the leakage channels (210) between the plates (150-180) of each of the heat exchanger elements (110, 120) are connected to no more than two leakage ports or to a single leakage port (230).

7. The double-wall plate heat exchanger (100) according to any of the preceding claims, wherein the leakage opening (230) is located on a short side of the rectangular heat exchanger element (110, 120).

8. 8. The double-wall plate heat exchanger (100) according to any of the preceding claims, wherein the plates (150-180) and the heat exchanger elements (110, 120) are rectangular and joined by brazing, and the long sides of the plates (150-180) are joined by a continuous brazing joint.

9. 9. The double-wall plate heat exchanger (100) according to any of claims 1 to 8, wherein the plates (150-180) are provided with peripheral skirts (S), the peripheral skirts of three consecutive plates (150-170) being formed with the leakage outlet (230) in the form of the openings to provide the common leakage outlet from the leakage channels (210) of two adjacent heat exchanger elements (110, 120).

10. The double-wall plate heat exchanger (100) of claim 9, wherein the openings are aligned.

11. 11. The double-wall plate heat exchanger (100) of claim 10, wherein three successive plates (150-170) having the openings aligned in the peripheral skirt (S) are followed by a plate (180) that does not have the openings corresponding to the peripheral skirt (S), thereby preventing any mixing of fluids leaking from adjacent flow paths (240).

12. The double-wall plate heat exchanger (100) according to any of the preceding claims, wherein the port openings (01-04) are arranged at different levels to provide the selective fluid communication between the flow paths (240).

13. The double-wall plate heat exchanger (100) according to any of the preceding claims, wherein a leak sensor is provided around the periphery of the heat exchanger plate to detect leakage from the leak opening (230).

14. The double-wall plate heat exchanger (100) according to any of the preceding claims, wherein the leakage channels (210) extend in the longitudinal direction of the plates (150-180), are arranged in parallel and are distributed across the width of the plates.

15. At least a first heat exchanger element (110) and a second heat exchanger element (120), The heat exchanger comprises at least a first heat exchanger element (110) and a second heat exchanger element (120), the first heat exchanger element (110) comprising a first plate (150) joined to a second plate (160), and the second heat exchanger element (120) comprising a third plate (170) joined to a fourth plate (180); the grooves (G) of the first plate (150) and the third plate (170) are provided with ridges (190) that cross the grooves (G), and the ridges (R) of the second plate (160) and the fourth plate (180) are provided with recesses (200) that cross the ridges (R); the recesses (200) and the ridges (190) cooperate to form the leakage channels (210) between the first and second plates (150, 160) and between the third and fourth plates (170, 180) to collect fluid leaking from the flow paths (240) between the first and second heat exchanger elements (110, 120); The double-wall plate heat exchanger (100) according to any one of claims 1 to 14, wherein the connection spaces (220) are provided between the first and second plates (150, 160) and between the third and fourth plates (170, 180).

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